The present invention relates to a final drive and differential unit for motor vehicles, and more particularly, but not exclusively, to a lubrication mechanism in the final drive and differential unit.
A final drive and differential unit is known of the type which comprises a differential carrier integrally formed with a cylindrical support structure and arranged to store an amount of lubricating oil therein, a differential gear unit rotatably mounted within the carrier, a ring gear contained within the carrier and mounted on the differential gear unit for rotation therewith, a drive pinion shaft supported by a pair of axially spaced bearings mounted within the cylindrical support structure, and in which the drive pinion shaft is integrally provided at the inner end thereof with a drive pinion in mesh with the ring gear and at the outer end thereof with a companion flange the sleeve portion of which is surrounded by an annular oil seal member within the outer end portion of the support structure to close the interior of the support structure in a fluid-tight manner.
In such a final drive and differential unit as described above, the inside bearing facing the interior of the carrier is directly splashed with lubricating oil picked up by rotation of the ring gear, but the outside bearing and the adjacent oil seal member may not be splashed with the picked up lubricating oil. It is, therefore, necessary to provide positive lubrication of the outside bearing and the adjacent oil seal member so as to ensure durability of the final drive and differential unit. In this respect, there has been proposed a lubrication mechanism for the outside bearing and the adjacent oil seal member, wherein an oil supply passage is formed in one side wall of the cylindrical support structure to receive the lubricating oil picked by rotation of the ring gear and to supply it into an annular space around the sleeve portion of the companion flange between the outside bearing and the oil seal member, and wherein an oil return passage is formed in the other side wall of the cylindrical support structure to permit the lubricating oil passing therethrough from the annular space to return into the interior of the differential carrier.
In the above lubrication mechanism, the cylindrical support structure is further integrally formed on the inner wall thereof with a guide portion which extends radially inwardly to store a predetermined amount of the lubricating oil within the bottom portion of the annular space for sufficient lubrication of the outside bearing and the oil seal member. In such an arrangement of the lubrication mechanism, it has been, however, observed that during stopping or low speed travel of the vehicle on an ascending road, the outside bearing allows the flow of lubricating oil passing therethrough from the annular space into the carrier. As a result, the liquid level of the stored lubricating oil in the annular space drops below a predetermined level, resulting in insufficient lubrication of the oil seal member.